The invention relates to adaptive compression of video signals for, e.g., PIP or double window display.
UK Patent Application GB-A-2,182,522, corresponding to U.S. Pat. No. 4,717,951, discloses an adaptive filtering system. A picture-in-picture television receiver, for which the viewer may change the size of the inset image, includes an adaptive anti-aliasing filter. The filter includes a variable delay element and an adder. Signals are applied to one input port of the adder and to the delay element. The signals provided by the delay element are applied to a second input port of the adder. The delay element provides time delays which may be expressed by the equation T=K1xcfx84+PK2xcfx84, where xcfx84 is a fixed amount of time, K1 and K2 are constants, and P is a variable. The frequency response characteristic of the filter is changed by a selection signal that changes the value of P.
It is, inter alia, an object of the invention to provide an adaptive filter having a simple control. To this end, a first aspect of the invention provides a method and device for video signal compression. A second aspect of the invention provides a display apparatus including such a video signal compression device.
In a video signal compression method in accordance with a primary aspect of this invention, compression ratio control signals and a previous sum are added to generate a new sum, compression control signals are logically generated in dependence upon the previous sum and the compression ratio control signals, and video signals are compressed in dependence upon the compression control signals to generate compressed video signals.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.